How to Install a Car Alarm in a Ford Focus

The Ford Focus is popular among customizers and installing a car alarm is a priority. Installing an alarm system on the Ford Focus requires considerable wiring skills and a clear understanding of car electronic systems. Popular options to include during this project are remote start and power window activation with more complex systems. Installing a basic alarm in the Ford Focus takes about two hours.

Read the alarm manual carefully and keep the technical support number for the alarm handy in the event you have questions. Open the hood and disconnect the positive battery cable. Connect the alarm power wire to the positive battery cable and run it along the firewall to the driver's side.

Mount the siren in an open area in the engine bay of the Focus, facing the engine to limit water contact while driving. Slide the driver's seat all the way back and remove the screws holding the bottom of the steering wheel case in place.

Identify the starter wire and attach the start disable relay. Connect the power lock module to the lock relay next to the fuse box. Drill a small hole in the dash for the LED light and snap it into place.

Install the shock sensor per the manual's instructions and pull the wires under the dash. Feed the power and siren wires through the firewall and connect them to the alarm control module. Attach the rest of the wires to the alarm module and secure it as far back into the dash as possible. On models prior to 2008 place the control module behind the radio for improved security.

Reconnect the positive battery cable and test the alarm. Adjust the sensitivity as necessary and secure any loose wires with zip ties.


2008 and later models of the Ford Focus use advanced data cabling requiring expert installation and special parts.

Things You'll Need

  • Alarm kit with vehicle wiring adaptors
  • Drill
  • Screwdrivers
  • Zip ties
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